Present electronic components require voltage regulation to successfully balance (“switch”) output voltage positions based on changing levels in load currents. A conventional control scheme for switching voltage regulation is pulse width modulation (PWM). For example, a PWM controller will drive a set of upper and lower gate output power switches in a synchronous power converter providing the voltage regulation. Typically, the output power switches are Metal Oxide Semiconductor Field-Effect Transistors, or MOSFETs.
Conventional PWM controllers will use a constant switching frequency, but vary a duty cycle of the upper and lower gate output power switches as the load currents vary. These controllers generally achieve good regulation, low noise spectrum, and high power efficiency. However, when load currents are low, these controllers are known to be inefficient due to switching losses experienced at the upper and lower gates, along with a high quiescent current (that is, a high output current exists when no signal is applied to the input of the power converter). It is known that by adjusting a switching frequency to compensate for varying load current conditions, the power efficiency at light load levels can be improved.
For example, in at least one improved switching frequency arrangement, the synchronous power converter normally operates in a continuous conduction mode (CCM), and will automatically enter into a diode emulation mode (DEM) at lighter load conditions. In this same example, the synchronous power converter operates as a synchronous voltage rectifier in the CCM mode. In the DEM mode, at least a lower gate MOSFET power switch attempts to remain OFF to block any negative current flow.
However, even by operating in the DEM mode at the lighter load conditions, the power converter continues to experience conduction losses at one or more of the MOSFET power switches that further reduces system efficiency of the power converter. Accordingly, there is a need for improvements in load current compensation in synchronous power converters.